Impactors for breakage of materials are known in the art. Such apparatus includes a rotating impeller device arranged to rotate about an axis. Feed materials such as rock, gravel, mineral ores and the like are passed into the rotating impeller device via an inlet. The materials are ejected from the impeller device to impact against a ring of anvils positioned on the inner surface of the surrounding walls of the impactor, and are thereby attritioned. Due to the nature of the feed materials and the duty required of the apparatus, the anvils are normally made of a high strength and abrasion resistant alloy metal or other materials and this is usually an expensive item. In use the anvils are subjected to significant and uneven wear over a period of time.